Combined telephone receiver and transmitter.



PATENTED AUG. 20, 1907.

' R. I. LUDLOW.

COMBINED TELEPHONE RECEIVER AND TRANSMITTER.

APPLICATION FILED APB..6,1904.

2 SHEE S-SHEET 1.

7 0 9 1 2 G U A D E T N E T A P W 0 L D U L R E COMBINED TELEPHONERECEIVER AND TRANSMITTER.

2 SHEETS-SHEET 2.

Finuenfoz APPLICATION TILED APR.6,1904.

WIN

from drcow warmam I 67 9 %/@M UNITED sTA ss RODNEY r.

PATENT OFFICE.

LUDLOW, OF PHILADELPHIA, PENNSYLVANIA.

COMBINED TELEPHONE RECEIVER AND TRANSMITTER.

Specification of Letters Patent.

Patented Aug. 20, 1907.

Application filed April 6,1904. Serial No. 201,794.

. To all whom it may concern:

My invention relates generally to telephone appara-.

tus and specifically to the transmitting and receiving apparatustherefor, the primary object of my invention being to unite in a singleconstruction or device, employing a single diaphragm or elasticsound-transmitter, means whereby the telephonic conversations may beboth received and transmitted.

In carrying out this primary purpose, my invention has for its objectsto mechanically and electrically unite in a single instrument receivingand transmitting means which shall be mutually helpful in order that thetransmitting mechanism shall increase thesound-producing effect of thereceived currents in the receiving mechanism; also that the receivingmechanism shall operate to increase the telephonic current given out bythe transmitting mechanism; also that the elements shall be so combinedthat a portion of the necessary mechanical structure for one shall servealso for the corre sponding structure of the other, resulting in a lessnumber of parts and a more compact single device than would otherwise bethe case if separate and distinct receiving and transmitting instrumentswere merely aggregated in a single casing.

The advantages resulting from my invention will be hereinafter brieflyreferred to, but among those which may now be stated are, the economy infirst cost resulting from consolidating a receiver and a trans mitter ina single device; and the great advantage to the operator in using it asa receiving instrument, in being able to hear the message transmittedwithout manually bringing the diaphragm holder to or against the ear.

To these ends my invention consists in the combination in oneinstrument, of a single diaphragm under tension, with means hereinafterdescribed, operating to conduct electrically-induced sound waves theretoand therefrom, respectively; the primary identifying fea tures of suchmeans comprising a suitably constructed casing and, within the same,concentric electro-magnetic and electric sound-transforming devices, adiaphragm common to both and arranged exterior to their electriccircuits, a variable resistance conductor in series with the windings ofthe magnet, with means common to the magnet and'the resistance, andinitially actuated by the vibrations of the diaphragm, operating toautomatically vary the magnetism of the former and alter the resistanceof the latter. These novel features together with the several minorcombinations of elements, hereinafter described and constituting theinvention in its best and preferred form, will be pointed out in theclaims.

In the drawings illustrating inv invcntion:Figure l is a sectional viewthrough tlncenter of my instrument as taken on the line 11 Fig. 3. Fig.2 is a section at right angles to Fig. 1 with the mouthpiece anddiaphragm removed. Fig. 3 is a plan view of Fig. 2

with the mouthpiece and diaphragm removed, to show more clearly theconstruction and arrangement of the remaining elements. Fig. 4 is asectional view of a modified form of the device, with the mouthpiece anddiaphragm removed. Fig. 5 is a detail section showing electricalconnections.

Similar letters ofreference indicate corresponding parts in the figures.

Referring to the drawings. A designates an annular ring havingprojecting flanges a a on either side of and of larger inside diameterthan the aperture a at the center. These flanges are threaded forattachment to corresponding threaded annular parts upon the main part ofthe case B and the mouthpiece C respectively. The portion of themouthpiece O fitting within the part A is provided on the side toward Awith two concentric annular depressions c c and a central aperture 0.Depression c is of larger diameter than the aperture a and depression 0is of diameter equal to that of a. Aperture c communicates with themouthpieceand is of diameter smaller than a. Glamped between A and G andlying within aperture 0 is a diaphragm D of any material susceptible tomagnetism. Upon the back or reverse end of the main part B is placed acap E closing central chamber b. This chamber communicates with the mainfront cylindrical compartment 12 through aperture 6 Within thecompartment B is located a magnet G energizing the pole pieces 9 g aboutwhich are windings g g. These windings are so connected that the samecurrent passes through both and tends to increase the magnetism in oneat the same time that it decreases the magnetism in the other.

ner usual to magnetic receivers.

Between the poles of the magnet is placed the transmitting mechanismwhich in the form illustrated in Figs. 1, 2 and 3 is constructed asfollows:Upon the casing of B within compartment B is provided 3. lug Hsplit at h and pierced by pin h. Upon this pin is pivot'ed the forkedarm J of any material having sufficient spring, one of whose projectingends j rests against the diaphragm preferably at or near the center. Theother end j thereof rests upon the top of the rod K. This rod passesthrough the aperture b and upon its rear end within the forward part ofrecess b carries an electrode L secured thereto by any suitable means asby nuts is k.

In the rear end of the rear recess b is another electrod'e L held inplace in the manner to be described oiin any suitable manner and restingagainst the cap E.

The magnets are placed in' proximity to the diaphragm and act upon it inthe manaffected by the same diaphragm.

Between the electrodes L and L is a spring M of general spiral formwhich tends to separate these electrodes and to prevent packing of thedivided carbon or other suitable resistance-varying medium N. Thechamber b may be provided with a lining 0 if desired. A conductor fromelectrode L leads up through the passageway P to finding post Q fromwhich outside connections are made as desired.

Between the ends of magnet G lies the switch R provided with contactblades 1' r and pivoted upon binding post S. It is connected in anysuitable manner to permit signaling when in the position shown in Fig.3. When at the extreme of its motion from that shown it makes connectionbetween binding posts '1 and U, to which one end of the magnet windingand the rod K are respectively electrically connected, thus throwing theelectric and electro-magnctic circuits, in other words, i to receivingand transmitting mechanisms into series connection. The other end of themagnet winding is connected through binding post V to the outsidecircuit in any suitable manner, the external connections being made withbinding posts S, V and Q through the openings W. a

In the form shown in Fig. 4 the fork arm I is omitted and therod K isextended to make contact with the diaphragm. In this case also thespiral spring is located within the larger forward compartment b insteadof b and is made to separate the electrodes by pressure against the bodyof B at one end and a disk X upon rod K at the other.

The mode of operation of mydevice is as follows:- When it is desired touse the transmitter and receiver, the switch R is turned so as to joinelectrically binding posts T and U, to which the rod K and winding g g'are connected, placing the magnet coils in series with the variableresistance conductor. Both are then Pulsations of current passingthrough the magnet coils attracting and, repelling the diaphragm withvarying strengths will also pass through the variable resistanceconductor but with little direct efiectupon it. The current fromthecommon or local battery also passes through these series connectionsand varies with direct effect upon the magnet coils according to thevariation of resistance in the circuit. All of the change of resistanceoccurs in the variable conductor and is due to variations in pressureupon it transmitted from the vibrating diaphragm through rod K due tothe voice or magnetic fluctuations and results in a change of currentthrough the magnet coils. The cause of this vibration may be eithersound vibrations or these electricalvibrations resulting in fluctuationsof magnetism.

It will thus be seen that if the current from the battery be in theproper direction anyattraction of the diaphragm due to an increase ofcurrent passing through the magnet coil will cause the diaphragm topress upon the-rod K causing a reduction of the resistance of thevariable conductor and a further increase of current strength in themagnet coils and still further attraction of the diaphragm until aposition of -equilibrium is reached between the increasing magnetism andthe more rapidly increasing resistance of the diaphragm to distortion.Since this increase of magnetism due to the joint action of batteryand'received currents is automatic in adjustment and instant in itsaction there will result-an increase in the volume of sound from thisinstrument when used as a receiver over that produced by an equalreceived current in a receiver having corresponding mechanical andmagnetic dimensions. As a transmitter, likewise, greater variations inresistance and hence stronger current will be caused by the same volumeof sound by reason of the action of the magnet whose magnetism isincreased by increased current through its coils and vice versa onaccount of the series arrangement before stated. As the diaphragmapproaches the magnet due to a sound wave in that direction tlie batterycurrent is increased. It flows through the magnet coils still furthermoving the diaphragm and intensifying the current. Hence the receivingand transmitting mechanisms, in conjunction with the diaphragm common toboth and constructed and combined therewith and with each other asdescribed, co-act both mechanically and electrically in the mannerstated, resulting in increasing the intensity and volume of sound wavesin respect of the receiving mechanism,

Having thus described my invention,v what I claim as new, and desire tosecure by Letters Patent, is:

1. in a telephone, a combined receiver and transmitter comprising asuitable casing, concentrically arranged electr0-magnetic and electricsound-transforming devices, a sin gle diaphragm common to both andarranged exterior to their electric circuits, with means to conductelectricallyinduced sound waves to and from said diaphragm, saidllll'ElHS comprising a variable resistance.conduct'or in series withtheiwindings of the magnet, and mechanism contacting with the diaphragmand operating to directly transmit its vibrations totheresistance-conductor.

2. In a telephone, a combined receiver and transmitter, comprising asuitable casing, with concentric electro-magnetic and electricsound-transforming devices, a single diaphragm common to both andarranged exterior to their electric circuits, a variable resistanceconductor in series with the windings of the magnet, a pair of separatedelectrodes, and connecting contact means between the diaphragm and oneof said electrodes, whereby on the pulsation of the diaphragmby'rcceivcd currents, the magnetic current is automatically increased bya reduction in the resistance of the variable conductor.

3. In a telephone, a combined receiver and transmitter comprising asuitable casing divided into'compartments, with concentricelectromagnetic and electric'sound-transforming devices, a singlediaphragm common to both and located outside their electric circuits, 8.bi-polar magnet in one of said compartments, a variable resistanceconductor between connected windings on the poles of the magnet, andmechanism between the diaphragm and the variable resistance conductorwhereby the resistance and the magnetism are mutually varied byautomatic operation of the transmitting me'ch'anism brought into actionby the pulsations of the diaphragm due to receivedcurrents.

4. In a telephone, a combined receiver and transmitter 7 comprising acasing containing two compartments, an elec-' sistance conductor inseries with the windingsthereoff, a

containing casing therefor comprising two compartments, one of themcontaining the magnet beldw the diaphragm and the other of themcontaining the resistance conductor below the magnet, 21 pair ofelectrodes in the same compartment and on. either side or the resistanceconductor, and means connecting one of said electrodes with thediaphragm whereby the resistance conductor is directly varied by thepulsations of the diaphragm.

6. In a telephone having a combinedreceiver and transmitter with asingle diaphragm exterior to the electric circuits, an electro magnet, avariable resistance in series with the windings thereof, with meanscommon to the magnet andvresistance, but exterior to their electriccircuits, operating to automatically vary the magnetism of the formerand to alter the resistance of the latter.

7. In a telephone a combined receiver and transmitter comprising anelectro-magnet, a carbon resistance in series with the winding thereof,a diaphragm, and a pivoted 1O elastic arm between the resistance and thediaphragm operating to transmit pulsations between them.

In testimony whereof, I have hereunto alfixed my signature this fourthday of April A. D. 1904.

RODNEY F. LUDLOW. Witnesses:

CHAS. W. MILLER, Emma E. SCHWARTZ.

